<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <!--  统计 object 中有多少个 key -->
    <script>
        
    var obj = {
        ect:'key',
        name:'小陈',
        age:18
    } 
    console.log(Object.keys(obj).length);
    

    </script>
</body>
</html>